【分治】动态点分治 （[ZJOI2007]捉迷藏）

  1 #include<bits/stdc++.h>
  2 #define INF 0x3f3f3f3f
  3 #define MAXN 100010
  4 using namespace std;
  5 inline int read ()
  6 {
  7     int w=1,s=0;
  8     char ch=getchar ();
  9     while (ch<‘0‘||ch>‘9‘){if (ch==‘-‘) w=-1;ch=getchar ();}
 10     while (‘0‘<=ch&&ch<=‘9‘) s=(s<<1)+(s<<3)+(ch^48),ch=getchar ();
 11     return s*w;
 12 }
 13 struct Heap{
 14     priority_queue<int>A,B;int size;
 15     Heap(){size=0;}
 16     void push (int x){A.push (x),size++;}
 17     void pop (int x){B.push (x),size--;}
 18     int top (){while (!B.empty ()&&A.top ()==B.top ()) A.pop (),B.pop ();return size?A.top ():-INF;}
 19     int len ()
 20     {
 21         if (size==0) return -1;
 22         if (size==1) return 0;
 23         int x=top ();pop (x);int y=top ();push (x);
 24         return x+y;
 25     }
 26     void op (int x,int c){c?pop (x):push (x);}
 27 }a[MAXN],b[MAXN],ans;
 28 struct edge{
 29     int v,w,nxt;
 30 }e[MAXN<<1];
 31 int n,q,cnt,root,sum,tot;
 32 int head[MAXN],size[MAXN],maxp[MAXN],s[MAXN],col[MAXN];
 33 int Fa[MAXN],dep[MAXN],son[MAXN],dist[MAXN],top[MAXN];
 34 bool used[MAXN];
 35 char opt[MAXN];
 36 void add (int u,int v,int w)
 37 {
 38     e[++cnt].v=v,e[cnt].w=w,e[cnt].nxt=head[u],head[u]=cnt;
 39 }
 40 void dfs1 (int u,int fa)
 41 {
 42     Fa[u]=fa,size[u]=1,dep[u]=dep[fa]+1;
 43     for (int i=head[u];i!=0;i=e[i].nxt)
 44         if (e[i].v!=fa)
 45         {
 46             dist[e[i].v]=dist[u]+e[i].w;
 47             dfs1 (e[i].v,u);
 48             size[u]+=size[e[i].v];
 49             if (size[e[i].v]>size[son[u]]) son[u]=e[i].v;
 50         }
 51 }
 52 void dfs2 (int u,int topf)
 53 {
 54     top[u]=topf;
 55     if (son[u]) dfs2 (son[u],topf);
 56     for (int i=head[u];i!=0;i=e[i].nxt)
 57         if (e[i].v!=Fa[u]&&e[i].v!=son[u])
 58             dfs2 (e[i].v,e[i].v);
 59 }
 60 int lca (int x,int y)
 61 {
 62     while (dep[top[x]]!=dep[top[y]])
 63     {
 64         if (dep[top[x]]<dep[top[y]]) swap (x,y);
 65         x=Fa[top[x]];
 66     }
 67     return dep[x]<dep[y]?x:y;
 68 }
 69 void getrt (int u,int fa)
 70 {
 71     size[u]=1,maxp[u]=0;
 72     if (!col[u]) s[++tot]=u;
 73     for (int i=head[u];i!=0;i=e[i].nxt)
 74         if (e[i].v!=fa&&!used[e[i].v])
 75         {
 76             getrt (e[i].v,u);
 77             size[u]+=size[e[i].v];
 78             maxp[u]=max (maxp[u],size[e[i].v]);
 79         }
 80     maxp[u]=max (maxp[u],sum-size[u]);
 81     if (maxp[u]<maxp[root]) root=u;
 82 }
 83 int f[MAXN];
 84 int getdis (int x,int y)
 85 {
 86     return dist[x]+dist[y]-(dist[lca (x,y)]<<1);
 87 }
 88 int divide (int u)
 89 {
 90     used[u]=1;if (!col[u]) b[u].push (0);
 91     for (int i=1;i<=tot;i++) a[u].push (getdis (f[u],s[i]));
 92     for (int i=head[u];i!=0;i=e[i].nxt)
 93         if (!used[e[i].v])
 94         {
 95             maxp[root=tot=0]=sum=size[e[i].v],getrt (e[i].v,0);
 96             f[root]=u;
 97             int child=divide (root);
 98             b[u].push (a[child].top ());
 99         }
100     ans.push (b[u].len ());
101     return u;
102 }
103 void modify (int x,int c)
104 {
105     int l1=b[x].len (),l2,s1,s2;b[x].op (0,c);
106     if (l1!=(l2=b[x].len ())) ans.pop (l1),ans.push (l2);
107     for (int u=x,fa=f[u];fa;fa=f[u=fa])
108     {
109         s1=a[u].top (),a[u].op (getdis (fa,x),c),s2=a[u].top();
110         if (s1!=s2)
111         {
112             l1=b[fa].len ();
113             if (s1!=-INF) b[fa].pop (s1);
114             if (s2!=-INF) b[fa].push (s2);
115             l2=b[fa].len ();
116             if (l1!=l2) ans.pop (l1),ans.push (l2);
117         }
118     }
119 }
120 int main()
121 {
122     n=read ();
123     for (int i=1;i<n;i++)
124     {
125         int u=read (),v=read ();
126         add (u,v,1);add (v,u,1);
127     }
128     dfs1 (1,0);dfs2 (1,1);
129     maxp[root]=sum=n,getrt (1,0);
130     divide (root);
131     q=read ();
132     while (q--)
133     {
134         scanf ("%s",opt+1);
135         if (opt[1]==‘C‘)
136         {
137             int x=read ();col[x]^=1;
138             modify (x,col[x]);
139         }
140         else printf ("%d\n",ans.top ()); 
141     }
142     return 0;
143 }